Update MacOS Runner

[CoolSpy3]

Description
GitHub recently deprecated the macos-11 runner, so all of the tests which rely on that os are failing. This PR updates the runner to the latest macos-14 macos-13 image. (There's some bug installing cppcheck on macos-14. I might play around with bumping the cppcheck version later, but I don't have enough info to resolve it as-is.)

Hopefully, most of the workflow can be ported without too much hassle, however, if that proves to not be the case, I may have to leave this fix for someone else, as I do not have a mac to debug on.

[CoolSpy3]

The build passes! I'll come back tomorrow and see if I can get cppcheck working. If not, I'll just revert to this commit.

SIde note: Even though the build runs on macos 13, it still targets macos 11. I assume that we want to keep that as-is because we do not want to drop old support unless it becomes necessary.

[omichel]

No, the plan is to support only the maintained versions macOS, that are currently 12 (Monterey), 13 (Ventura) and 14 (Sonoma). So we should drop macOS 11 Big Sur and update the requirements documentation accordingly.

[CoolSpy3]

We've done it! This PR is ready for review!
A summary of the changes:

• Updated the macos runner to version 14
  • Once this PR is merged, I can migrate this change to the wiki
• Removed support for macos 11
• Bumped cppcheck to version 2.14.1
• Updated the system requirements to reflect the above
• Updated the changelog

Notes on reviewing/merging:

• It may be helpful to review just the config changes (also Serial.cpp) and just the warning fixes individually. Luckily, the warning fixes are all very small; there's just a lot of them.
  • You can also review them commit-by-commit, which could make it easier to review some smaller changes separate from the ones which just add const in front of everything.
• In order to pass the merge requirments, the required macos-11 "Test Sources" check should be replaced with the new macos-14 variant.

[omichel]

Very good job! Thank you!
I could review all the file changes as per your instructions and everything looks very good to me.
I like your approach of adding some cppcheck-suppress comments instead of trying to fix the problem when it was not super obvious to fix as it minimizes the risk of introducing some bugs, while still highlighting possible improvements.
I just replaced the mandatory macos-11 "Test Sources" check with the new macos-14 one.
I just have one minor suggestion, but you can ignore it if you prefer.